The present invention relates to systems involving inductive radio, particularly to position locating systems utilizing inductive radio. These systems make it possible to detect and control mobile objects, such as a train, travelling crane, etc., on running tracks. In container yards of wharfs, for instance, the installation of conventional multi-wire type lines for radio-frequency is not practical since it requires under-ground construction. In such cases a relative position locating system may be used which counts the number of crossings in the twisted-pair type inductive radio-frequency lines.